However, there are several ways to interrupt the power supply, which might be what you're looking for:
* Battery Negative Terminal: Disconnecting the negative (-) terminal of the battery will cut power to the entire vehicle. This is the most reliable way to completely shut down all electrical systems. You'll need a wrench to loosen the terminal clamp.
* Main Power Relay (Less Common): Some vehicles have a main power relay that, when removed, cuts power to most systems. The location of this relay varies significantly between vehicles and even model years, so finding it would require consulting a wiring diagram for your specific Astrovan. This is not a typical method for casual use.
* Ignition Switch: The key itself is the main power switch for the engine.
Important Note: Disconnecting the battery or tampering with the electrical system should only be done by someone familiar with automotive electrical systems to avoid damage or injury. If you're not comfortable with this, take your van to a qualified mechanic.
